Chemical Elements and the Laws of Nature

We are amazed to realize that everything in the world around us is made up of fewer than 100 different chemical elements. Those elements are combined to form vast numbers of different compounds, and those compounds come together to make up everything including air, soil, plants, and our bodies.

Even more amazing is that those chemical elements are all made up of the same three particles called protons, electrons, and neutrons. The only difference between the elements is the quantity of each of the particles in their atoms. The periodic table gives an organized way to look at the elements based on the number of protons in the nucleus of each atom. It shows all of the natural elements plus more than 20 others that have been created in laboratories with particle accelerators–machines that smash atoms together.

The natural chemical elements range from hydrogen with only one proton to uranium which has 92. The periodic table, first conceived in the nineteenth century, shows which elements react similarly with other elements to form chemical compounds. The ability of the various elements to combine with other element makes possible every compound which makes up every substance on Earth.

Each atom of each element has protons in the center called a nucleus and electrons surrounding the nucleus in “shells.” The atoms of some elements also have neutrons in the nucleus. The strong interaction in the nucleus binds the protons and neutrons together. At the same time, the electrical or Coulomb force causes the protons to repel each other. As the number of protons approaches 100 or more, the repelling force overcomes the attracting force, and the atom becomes unstable. For that reason, the larger atoms only exist in the laboratory and only for very short times.

If you could add the mass of all of the protons, neutrons, and electrons in an atom, you would find that the total mass is more than the mass of the atom itself. That extra mass is found in the energy that binds the nucleus together. Einstein’s famous equation E=mc^2 indicates that matter and energy are different forms of the same thing. In other words, the extra mass has become the energy that binds the nucleus together.